Method for the powder-metallurgical production of components from titanium or titanium alloys

ABSTRACT

A method for the powder-metallurgical production of a component from titanium or a titanium alloy is disclosed. In this method, following the customary procedure, first a green part is formed by using metal powder formed from titanium or the titanium alloy and is densified and compacted in a subsequent sintering step. Metal powder of titanium or the titanium alloy with an average grain size of &lt;25 μm is used for producing the green part and the sintering step is carried out at a sintering temperature of up to a maximum of 1100° C. for a sintering at a sintering duration of ≤5 hours in an atmosphere that is under a reduced pressure in comparison with normal pressure. These measures achieve the effect that the grain structure of the material obtained, and consequently also the material properties, can be selectively influenced.

TECHNICAL FIELD

The present invention relates to a method for the powder-metallurgicalproduction of a component from titanium or a titanium alloy, whereinfirst, using metal powder produced from titanium or the titanium alloy,a green part is formed and this is densified and compacted in asubsequent sintering step.

BACKGROUND Background Information

Various powder-metallurgical methods for producing true-to-size titaniumcomponents (here and in the following, “components from titanium” willbe used here and in the following as a simplified term for componentsmade from titanium (pure titanium) or one or more titanium alloys) areknown, where in all methods, first a green part is produced, and this isdensified and compacted in a subsequent sintering step. The green partcan be produced in various ways, especially using additive productionmethods, metal powder injection molding, extrusion methods andnon-pressurized powder-metallurgical production methods.

Because of the excellent properties of the material, titanium, plus theefficient and economical production method, the powder-metallurgicalproduction of titanium is becoming increasingly more widely used. Thegood biocompatibility and the high specific strength of the material,titanium, play an important role especially in applications in medicalengineering and air and space technology. The economically mostsignificant alloy with sales figures accounting for more than 50% of thetotal titanium market I Ti6Al4V.

As a rule, the following steps must be executed to produce apowder-metallurgically processed titanium component:

-   -   a) forming    -   b) debinding    -   c) sintering

The objective of forming is to bring the titanium powder particles intothe tightest possible packing in a form close to the final contour. Inthis step, depending on the method employed, additives are used whichmust be removed in one or more subsequent debinding step(s). In thesubsequent process step, frequently also the final one, sintering, thepowder particles are consolidated by material transport.

Because of the high reactivity of titanium, all processing steps musttake place under special process conditions. In patent EP 1 119 429 B1[1], Gerling et al. describe necessary process conditions for sinteringtitanium. The combined implementation of debinding and sintering in acombined furnace design is described by Blum in EP 1 496 325 A2 [2].

Titanium has two crystal modifications. The hexagonal a phase, whichwith pure titanium and normal pressure is present up to a temperature of882.5° C., and the cubic space-centered β phase, which with puretitanium and normal pressure occurs above the aforementionedtemperature. The presence of the different phases at room temperature isused to classify titanium alloys into α-Ti, (α+β)-Ti and β-Ti alloys.Ti6Al4V, for example, is an (α+β)-alloy, i.e., both phases are presentin the grain structure at room temperature. To produce components with agenerally desired density >97% in the process of sintering titanium andtitanium-alloy components, sintering temperatures of about 1100-1400° C.at a sintering duration of about 2-5 h are needed. For pure titanium andTi6Al4V this means that the materials are processed in the p-phaseregion, which leads to a massive p-grain growth.

In EP 1 119 429 B1 [1], Gerling et al. describe that the grain structurethat becomes established has a p-grain growth of about 150 μm. Here, thenomenclature according to Sieniawski et al. [3], shown in FIG. 1, isused to describe the sizes of the various structures in the lamellar(α+β) alloys. The following designations are used:

-   -   D: grain size of the primary β phase    -   d: the size of a parallel α-lamella colony    -   t: the width of an α-lamella

In contrast to reforming processes, forming takes place as the firststep on the powder metallurgy route. In the next process step,sintering, the compacted titanium alloy, previously brought into shape,is produced. In contrast to standard processing approaches, because ofthe reverse sequence of the process steps (1. forming, 2. materialconsolidation) in the powder metallurgy approach, the possibility ofrefining or optimizing the grain structure of the metal and thus itsmaterial properties by thermal/mechanical working before the formingstep does not exist. For powder-metallurgical methods for producingcomponents from titanium and/or titanium alloys, precisely theprocess-determined inverse sequence, combined with the very limitedinfluence on the grain structure that develops during the familiarsintering process, is a limiting factor. As an example: the grainstructure of a Ti6Al4V sample produced in the standard manner fromtitanium powders commonly used in the prior art (with powder grain sizes≤45 μm) and sintered under sintering conditions typically used in theprior art is shown in FIG. 2. Here it is possible to recognize thetypical lamellar mixed grain structure for titanium components producedin the known way by powder metallurgy and sintered, made up of α phasesand β phases, the (α+β) grain structure, with a mean primary β-phasegrain size (D) of about 190 μm.

The production of powder-metallurgically processed titanium and titaniumalloys with small grain sizes is described in U.S. Pat. No. 4,601,874[4] by Marty et al. Through the targeted admixtures of S, P, B, As, Se,Te, Y and lanthanoids, during the consolidation process a material isproduced with grain sizes smaller by two orders of magnitude than thetitanium powder particles used. The drawback of this approach is thatthe use of titanium and titanium alloys is widespread precisely instrictly regulated market segments. For these application purposes, thechemical compositions of the material and its mechanical properties areregulated by standards. For example, the material is compositions andmechanical properties of Ti6Al4V and pure titanium are regulated in thestandards ASTM F2885 and ASTM F2889 respectively.

An additional procedure for producing fine-grained titanium and suchtitanium alloys by powder metallurgy is described in WO 2012/148471 A1.Here a green part made from titanium (alloy) powder with grain sizes ofless than 325 mesh (less than 44 μm) is produced and then subjected to amultistep process of compaction and forming. In a first step the greenpart is sintered in a hydrogen atmosphere at temperatures of 1100 to1500° C.; in the embodiments, the processing temperature is always givenas 1200° C. In this process titanium material in the β-phase forms. In asubsequent step of controlled cooling, a phase transformation occurs, inwhich restructuring occurs in the β-grains, resulting in a phase mixtureof fine α-grains, β-grains and δ-phases. Then in a final step, thehydrogen must be expelled from the component obtained, which is done byapplying a vacuum. With this procedure especially the use of hydrogen isespecially problematic, since this gas can only be expelled from thecomponent with great effort and often not completely expelled. Negativeeffects on the material properties and the stability of the materialhave been blamed on hydrogen remaining in the grain structure of thematerial. Outgassing from residual hydrogen from the finished componentin various applications is also anything but desirable.

SUMMARY

One goal generally pursued with the invention is that of creating thepossibility, is in the case of powder-metallurgically produced andsintered titanium components, of manipulating the grain structure andoptimizing the material properties. In particular the intention was tomake it possible to adapt the material properties to the specific usecase directly in the sintering process and/or to create, during thesintering process, an optimal starting point for further thermaltreatment steps after sintering. For example, it should be possible, bymodifying the sintering conditions, to create a primarily globular grainstructure with high ductility.

To solve the problem, a process is suggested that comprises a method forthe powder-metallurgical production of a component from titanium or atitanium alloy, wherein first, using metal powder from titanium or thetitanium alloy, a green part is formed and this is densified andcompacted in a subsequent sintering step, characterized in that forproducing the green part, metal powder from titanium or titanium alloywith a mean grain size of <25 μm, measured using laser diffractionaccording to ASTM B822-10 is used and that the sintering step isperformed at a sintering temperature up to a maximum of 1100° C., at asintering duration of <5 h in an atmosphere under a reduced pressure incomparison with normal pressure. Advantageous embodiments of theinvention are that the maximum grain size of the metal powder fromtitanium or the titanium alloy is <30 μm; that the sintering step isperformed under a vacuum with a pressure of 10⁻³ mbar, especially at apressure of 10⁻⁵ mbar; and that the sintering step is performed in aninert gas atmosphere, especially an argon atmosphere, at a pressure of<300 mbar. For producing the green part, metal powder from titanium orthe titanium alloy with a mean grain size of <20 μm, in particular of<10 μm, preferably of <5 μm, is used. The sintering duration is 3.5 h,in particular of s 3 h, preferably of ≤2.5 h. Furthermore, the sinteringduration is at least 1 h, preferably at least ≤2 h. The sinteringtemperature is up to a maximum of 1050° C., preferably up to a maximumof temperature up to a maximum of 1000° C., especially up to a maximumof 950° C. and the sintering temperature amounts to at least 860° C. Themethod is further characterized in that in the sintering step, thesintering temperature is adjusted in the range below a β-transitiontemperature of the titanium or titanium alloy material. The componentafter the sintering step has a material density of >97%, inparticular >98%, preferably 99%. In the sintering step, a sinteringtemperature of below 950° C. is selected and that to achieve a materialdensity in the component of >97%, after the sintering step this isexposed to an additional step with pressure and optionally atemperature, e.g., a step of cold isostatic pressing (CIP) and/or hotisostatic pressing (HIP). The component, following the sintering step,is subjected to a thermal aftertreatment that is conducted in the formof one or more of the following treatment procedures: hot isostaticpressing (HIP), quench, uniform rapid quench (URQ). An additional aspectto solving this problem lies in a titanium component that exhibits theproperties that it has a globular α-structure with a grain size of <30μm; that it has a grain structure with globular α-structure with meangrain size of <30 μm and lamellar (α+β) grain structure with a meanprimary β-phase grain size of <90 μm; and/or that it has a lamellar(α+β) grain structure with a mean primary to β-phase grain size of <120μm.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The figures show:

FIG. 1 a representation of a lamellar (α+β) grain structure of a Ti6Al4Vsample with description of the gran structure fractions according toSieniawski et al. [3];

FIG. 2 an enlarged photomicrograph of a standard sintered Ti6Al4Vsample, produced by powder-metallurgically using powder particles <45 μmand standard-sintered and confirms a lamellar (α+β) grain structure forthis;

FIG. 3 a schematic representation of the effect of reducing the grainsize by half (using the example of spherical particles) on the number ofparticles required to fill a defined volume;

FIG. 4 a schematic representation of the reduction in size of the hollowspace between adjacent particles due to reducing the grain size by half(using the example of spherical particles);

FIG. 5 an enlarged polished micrograph section of apowder-metallurgically produced and sintered Ti6Al4V sample made frompowder particles <20 μm, confirming the formation of a distinct globularα-structure; and

FIG. 6 an enlarged polished micrograph section of apowder-metallurgically produced and sintered Ti6Al4V sample made frompowder particles <20 μm, confirming the formation of a bimodal grainstructure with a globular α-structure and distinct lamellar (α+β) grainstructure.

DETAILED DESCRIPTION

An essential prerequisite for implementing the process according to theinvention and creating the possibility of influencing the materialproperties in the sintering process is the use of metal powder, producedfrom titanium or a titanium alloy, with a mean grain size of <25 μm,so-called fine powder. In such fine powder used for the processaccording to the invention, the maximum grain size may in particular be<30 μm. The maximum grain size is specified as a limit value by themanufacturers of such fine powders. At the same time, a small fractionof particles in such batches can always have grain sizes above thislimit. Such a fraction, as a rule, is generally specified as a maximumof 1 to a maximum of 5 wt.-%.

The mean grain size may advantageously even be lower, especially <20 μm,advantageously <10 μm and particularly preferably even <5 μm. Thesmaller the grain size of the metal powder is, the more readily highfinal densities can be achieved even at sintering temperatures markedlyreduced compared to the relatively high sintering temperaturespreviously used.

The measurement of the grain sizes essential for the invention and thedistribution thereof is performed by grain size testing using laserdiffraction according to ASTM B822-10 (published 2010), valid at thetime of this application. The grain size distribution is determined bywt.-% and according to D10/D50/D90, wherein D50 is the mean grain size.Specifically, the grain sizes given here in comparison tests weremeasured using the COULTER® LS grain size analyzer made by BeckmanCoulter and evaluated using the Fraunhofer theory according to ASTMB822-10.

For spherical particles, the grain size in the sense of the invention isspecified as the particle diameter. For nonspherical particles, thegrain size corresponds to the projected maximum particle dimension.

As a result of the reduced grain size, the surface area in thenonconsolidated component available for the sintering process increases,and thus so does the stored surface energy. Since the reduction of thisenergy is the driving force in the sintering process, the sinteringprocess can then take place using little thermal energy.

An additional advantage of using fine powders of the sizes indicatedabove for forming the green part is that more powder particles can beintroduced per unit volume. In addition to the enlarged surface, thisleads to a higher number of contact points per unit volume, as shown inFIG. 3. There, in a schematic representation, the effect of reducing thegrain size by half (using the example of spherical particles) on theparticle count to fill a defined volume is shown.

The contact points of the particles in turn are the starting point and anecessary condition for the sintering process, which is driven bydiffusion processes. The increased number of such contact points perunit volume therefore improves the starting conditions for the sinteringprocess.

Through the use according to the invention of fine powders with meangrain sizes <25 μm, when considering the ideal packing density inaddition to the aforementioned advantages, the result also occurs thatthe volume enclosed by the powder particles, as shown in an idealizedrepresentation in FIG. 4, is decreased. In FIG. 4, in a schematicrepresentation the decrease in size of the hollow space between adjacentparticles is illustrated by reducing the grain size by half (using theexample of spherical particles). Since this hollow space must be closedto achieve the—high—material density desired for the component followingthe sintering process must be closed by material transport during thesintering process, a smaller volume to be covered is an additionaldecisive reason for an improvement in the process result.

The sintering step typically takes place in a reduced-pressureatmosphere. This can be a vacuum with a pressure of ≤10⁻³ mbar,especially 10⁻⁵ mbar. However, it may also be a reduced-pressure inertgas atmosphere with a pressure of, e.g., 300 mbar. Argon gas inparticular is considered as the inert gas here.

The sintering temperatures according to the invention are below 1100° C.They can in particular be a maximum of 1050° C., a maximum of 1000° C.,and even a maximum of only 950° C. Preferably, however, to achieve agood sintering result, the sintering temperature selected advantageouslyshould not be below 860° C. The sintering temperature may be keptuniform. In particular, however, it is also possible and falls withinthe meaning of the invention to vary the temperature during thesintering process. The sintering temperature is defined here as thetemperature that the workpiece to be sintered has undergone. Dependingon the sintering unit, in the unit control, an adapted processtemperature is to be selected, which distinguishes the processtemperature measured at a distance remote from the workpiece from thesintering temperature undergone by the workpiece.

The duration of sintering may especially be ≤3.5 h, often also ≤3 h oreven ≤2.5 h. However, it was found that as a rule, for achieving goodresults, the sintering time should amount to at least 1 hour, preferablyat least 2 hours.

After the sintering step, components from titanium or titanium alloysproduced with the method of the invention generally have a final densityof >97%. However, final densities above 98% may also be reached, even≥99%.

To achieve a globular grain structure, the titanium components aresintered at less than the β-transition temperature (e.g., at atemperature 30° C. below the β-transition temperature.

For example, in initial experiments at a sintering temperature of 950°C., which is below the β-transition temperature, and with a sinteringduration of less than three hours, components with a final densityof >97% were produced. These had a globular grain structure with anα-grain size on average of 10.1 μm and a max. size of 29 μm. The grainstructure of this material is shown in FIG. 5. These grain sizes fall inthe order of magnitude of the powder particles used.

According to the literature, the β-transition temperature of Ti6Al4Vfalls in the range of 985° C. to 1015° C. [3; 5]. This relatively widerange given in the literature is attributable, on one hand, to thedistribution of the alloying elements in the titanium alloys. On theother hand, the ambient pressure is an additional influential factor.For example, Huang et al. describe that as a result of elevated processpressures (1500 bar), a reduction of the α-transition temperature can beobserved in the alloy Ti4Al8Nb [6].

The inventors now believe that depending on the process conditions,shifts in the β-transition temperature of only a maximum of 20° C. willbe observable due to pressure variations.

For creating a bimodal structure, the components were sintered close tothe β-transition temperature, but still below this.

For example, in order also to produce the lamellar grain structure withreduced primary β-phase grain size of the Ti6Al4V alloy, which is alsoadvantageous for many use cases, initially samples were produced inwhich the titanium components were sintered at a sintering temperatureof 1000° C. (FIG. 6). As shown by studies of the samples obtained withrespect to the grain structure formed, this sintering temperature wasstill below the β-transition temperature, although only slightly. Thebimodal grain structure formed is composed of globular α-structure andsmall portions of lamellar (α+β) structures, wherein the mean β-grainsize is 81 μm.

The density measurement was performed according to the specifications ofASTM B962 and ASTM B311. The grain size determination was performedaccording to the provisions of ASTM E112.

For creating a lamellar grain structure with the smallest possible grainsize of the primary β-phase grains, the components were largelysintered, i.e., for the greatest part of the time, below theβ-transition temperature, but with a minimal hold time that remainedbelow 30 min, preferably below 20 min, especially below 10 min, and alsoabove the β-transition temperature in phases, so that the p-phase isentirely present, in order thus to create the lamellar grain structure,but also the primary β-phase grain does not exceed the size range of aglobular α-structure with mean grain size of <30 μm and lamellar (α+β)grain structure with a mean primary p-phase grain size of <90 μm. Thesintering above the p-transition temperature always took place at atemperature in excess of 1015° C. This temperature was always kept below1080° C., but advantageously was below 1040° C. and especially ≤1020° C.was selected.

The possibilities mentioned above for influencing the phase compositionin the sintered material by systematic adjustment of the sinteringconditions at sintering temperatures below 1100° C., especiallyprimarily below the β-transition temperature, present a particularadvantage of the process according to the invention. The prerequisitefor this variability is that sufficiently compact titanium componentscan be produced below the β-transition temperature, which is possible,as the inventors recognized, based on the use of the fine powder,essential to the invention, with grain sizes below <30 μm.

Thus it has been shown that according to the method of the invention,powder-metallurgical moldings from titanium and titanium alloys can besintered at sintering temperatures below the usual mark of beyond 1100°C., generally 1200° C. or more, advantageously below the p-transitiontemperature, and thereby components with good structural and othermaterial properties can be obtained. It was possible to show that atdistinctly lower set sintering temperatures compared with the sinteringtemperatures customary in the prior art—unexpectedly—components withhigh final densities of >97% can be obtained. In particular it was shownthat the method according to the invention makes it possible to vary thegrain structure of the titanium component in the sintering process anddrastically reduce the grain size, which makes it possible to optimizethe mechanical properties of the components, e.g., the tensile strength,ductility and fatigue strength.

For example, within the scope of the invention, a particularly lowtemperature may also be selected for sintering, e.g., a temperaturebelow 950° C., can be selected, and if the desired material density inthe finished component (generally >97%) is not yet achieved in such asintering step, further compaction of the material can be performed inthe subsequently performed pressing step, in which the material issubjected to pressure and optionally a temperature, especially by coldisostatic pressing (CIP) or hot isostatic pressing (HIP). Here, forexample, the material density after sintering may be at <97%, and it maybe compacted to >97% by the pressing step after sintering.

In addition, following the sintering step, components produced accordingto the method of the invention may be subjected to additional thermalaftertreatments to further modify the properties of the materials. Suchadditional thermal aftertreatments can, for example, be one or more ofthe following methods: hot isostatic pressing (HIP), quench, uniformrapid quench (URQ).

The lower sintering temperature compared to the sintering temperaturesfrom the prior art also result in additional environmental/financial andprocess technology advantages. On one hand, less thermal energy isrequired in the sintering process, leading to lower costs but also toshorter processing times. On the other hand, the method in accordancewith the invention performed with reduced sintering temperature alsoallows the use of how-wall furnace designs which are once again moreeconomical than furnaces designed for process temperatures >1100° C.,where cold-wall furnaces are typically used.

The selective combination of fine powders with mean grain size <25 μm,preferably also with maximum grain sizes <30 μm, and reduced sinteringtemperatures compared with the prior art, to be classified as low,allows the unrivaled manipulation of the grain structure and thus of thematerial properties.

REFERENCES

[1] R. Gerling, T. Ebel, T. Hartwig: Method for producing components bymetal powder injection molding. European patent EP1119429B1, 2003.

[2] H.-J. Blüm: Method for combined debinding and sintering ofglass-ceramic, ceramic and metal molded parts. European PatentEP1496325A2, 2004.

[3] J. Sieniawski, W. Ziaja, K. Kubiak, M. Motyka: Microstructure andMechanical Properties of High Strength Two-Phase Titanium Alloys.Materials Science/Metals and Nonmetals “Titanium Alloys—Advances inProperties Control,” 2013, ISBN 978-953-51-1110-8.

[4] M. Marty, H. Octor, A. Walder: Process for forming a titanium basealloy with small grain size by powder metallurgy. U.S. Pat. No.4,601,874, 1986.

[5] J. Lindemann: Titanium alloys, Laboratory Course on LightweightConstruction Materials, Department of Metals Science and MaterialsTechnology Brandenburg Technical University Cottbus, 2012.

[6] A. Huang, D. Hu, M. H. Loretto, J. Mei, X, Wu: The influence ofpressure on solid-state transformations in Ti-46Al-8Nb. ScriptaMaterialia, Vol. 56, 4^(th) Ed., 2007, p. 253-324.

1. A method for the powder-metallurgical production of a component fromtitanium or a titanium alloy, wherein first, using metal powder fromtitanium or the titanium alloy, a green part is formed and the greenpart is densified and compacted in a subsequent sintering step, whereinfor producing the green part, metal powder from titanium or titaniumalloy with a mean grain size of <25 μm, measured using laser diffractionaccording to ASTM B822-10, is used and the sintering step is performedat a sintering temperature up to a maximum of 1100° C. in an atmosphereunder a reduced pressure in comparison with normal pressure.
 2. Themethod according to claim 1, wherein the maximum grain size of the metalpowder from titanium or the titanium alloy is <30 μm.
 3. The methodaccording to claim 1, wherein the sintering step is performed under avacuum with a pressure of ≤10⁻³ mbar.
 4. The method according to claim1, wherein the sintering step is performed in an inert gas atmosphere ata pressure of ≤300 mbar.
 5. The method according to claim 1, wherein forproducing the green part, metal powder from titanium or the titaniumalloy with a mean grain size of <20 μm is used.
 6. The method accordingto claim 1, wherein the sintering duration is ≤3.5 h.
 7. The methodaccording to claim 1, wherein the sintering duration is at least 1 h. 8.The method according to claim 1, wherein the sintering temperature is upto a maximum of 1050° C.
 9. The method according to claim 1, wherein thesintering temperature amounts to at least 860° C.
 10. The methodaccording to claim 1, wherein in the sintering step, the sinteringtemperature is adjusted in the range below a p-transition temperature ofthe titanium or titanium alloy material.
 11. The method according toclaim 1, wherein the component after the sintering step has a materialdensity of >97%.
 12. The method according to claim 1, wherein in thesintering step, a sintering temperature of below 950° C. is selected andthat to achieve a material density in the component of >97%, after thesintering step the component is exposed to an additional step withpressure and optionally a temperature.
 13. The method according to claim1, wherein the component, following the sintering step, is subjected toa thermal aftertreatment.
 14. The method according to claim 13, whereinthe thermal aftertreatment is conducted in the form of one or more ofthe following treatment procedures: hot isostatic pressing (HIP),quench, and uniform rapid quench (URQ).
 15. A component producedaccording to claim 1 from titanium or a titanium alloy having a globularα-structure with a grain size of <30 μm.
 16. A component producedaccording to claim 1 from titanium or a titanium alloy having a grainstructure with globular α-structure with mean grain size of <30 μm andlamellar (α+β) grain structure with a mean primary β-phase grain size of<90 μm.
 17. A component produced according to claim 1 from titanium or atitanium alloy having a lamellar (α+β) grain structure with a meanprimary β-phase grain size of <120 μm.
 18. The method according to claim3, wherein the sintering step is performed under a vacuum with apressure of ≤10 ⁻⁵ mbar.
 19. The method according to claim 4, whereinthe sintering step is performed in an argon atmosphere.
 20. The methodaccording to claim 5, wherein metal powder from titanium or the titaniumalloy with a mean grain size of <10 μm is used.
 21. The method accordingto claim 20, wherein metal powder from titanium or the titanium alloywith a mean grain size of <5 μm is used.
 22. The method according toclaim 6, wherein the sintering duration is ≤3 h.
 23. The methodaccording to claim 22, wherein the sintering duration is ≤2.5 h.
 24. Themethod according to claim 7, wherein the sintering duration is at least≤2 h.
 25. The method according to claim 8, wherein the sinteringtemperature is up to a maximum of 1000° C.
 26. The method according toclaim 25, wherein the sintering temperature is up to a maximum of 950°C.
 27. The method according to claim 11, wherein the component after thesintering step has a material density of >98%.
 28. The method accordingto claim 28, wherein the component after the sintering step has amaterial density of ≥99%.
 29. The method according to claim 12, whereinthe additional step with pressure comprises one of cold isostaticpressing (CIP) and hot isostatic pressing (HIP).
 30. The methodaccording to claim 1, wherein the sintering step is performed for asintering duration of ≤5 h.